Question

The first five terms of a sequence are shown below.

5, 9, 13, 17, 21

If the nth term of this sequence is represented by f(n), which of the following functions best represents this sequence?

f(n) = 5n - 1; n ≥ 1

f(n) = 5n + 1; n ≥ 1

f(n) = 4n - 1; n ≥ 1

f(n) = 4n + 1; n ≥ 1

Answer 1

@Loser66 I think D.

Answer 2

I think it is D because it is adding four every time...

Answer 3

I didn't understand - sorry.

Answer 4

...

Answer 5

This is an arithmetic progression, with the first term 5 and common difference: 4.

The nth term of the sequence: a, a + d, a + 2d, a + 3d, ..... is:
a + (n-1)d

Answer 6

Okay so the first term would be a?

Answer 7

Yes. The first term is a. Here a = 5.
The common difference is d. Here d = 4.
Put it in the formula for the nth term and simplify.

Answer 8

So the answer would be A?

Answer 9

No. Put a = 5, d = 4 in a + (n-1)d and simplify.

Answer 10

5 + (n - 1)4
5 + 4n - 1

Answer 11

No. 5 + (n - 1)4 = 5 + 4n - 4 = 4n + 1

Answer 12

So D?

Answer 13

lol u so confused

Answer 14

i know ^

Answer 15

why dont you just google it

Answer 16

Yes, D.

Answer 17

ahhhhhhhahaa u were right nice lol peace

Answer 18

phew.

Answer 19

It is simple to verify too. Just put n = 1, 2, 3, .... in 4n + 1 and see if you get each term of the sequence.